A casting technique for molding a product using a casting mold is a technique capable of producing products in large quantities with a consistent shape and quality, and is used in manufacturing products using a variety of materials. In the casting process, a die lubricant is generally applied to a molding surface of the casting mold, by which the product is released more easily when the molded product is to be removed from the casting mold. However, when casting is repeated, the material may stick to the casting mold, and removing the product from the casting mold becomes more difficult.
For example, when aluminum alloy, etc. is to be cast by a die casting method, molten aluminum is filled rapidly into a metal cavity under high pressure. Molten metal may stick to the portion of the casting mold making contact with the molten aluminum, and release resistance upon ejecting the product from the casting mold increases.
This problem can be resolved by covering the surface of the casting mold with a carbon film. The carbon film prevents the molten metal and the base material of the casting mold from making direct contact, suppressing the sticking of molten metal to the casting mold and an increase in release resistance. For example, in Patent Document 1, carbon material having fullerenes as its principal component is rubbed onto the surface of the casting mold used for aluminum die casting. This formed carbon film having fullerenes as its principal component on the surface of the casting mold reduces release resistance and prevents from sticking.